1. Field of the Invention
The present invention relates to a wave power generation device which generates electric power by extracting energy from a wave through movement of a float floating on the sea and a method of controlling the same.
2. Description of related art including information disclosed under 37 CFR §§1.97 and 1.98
Conventionally, there has been a wave power generation device with a float floating on a sea surface or in the sea (see Patent Literature 1, for example). FIG. 9 shows an example of a conventional wave power generation device. The wave power generation device 1X includes: a column 2X moored by an anchor 31 installed on a sea floor and a mooring line 32; and a float 3X floating on a sea surface 10 by receiving buoyancy. The float 3X is configured to receive a force of a wave and move up and down relative to the column 2X (see the arrow in FIG. 9).
Moreover, the wave power generation device 1X includes a frame body 5X for transmitting the movement of the float 3X to a power generator (not shown) installed in the column 2X. Furthermore, the wave power generation device 1X may also include a buoyancy adjustment part 33 for adjusting the position of the wave power generation device 1X in the vertical direction in the sea. This conventional float 3X has a point symmetric shape about the column 2X, such as a disc shape or a cylindrical shape, for example, and specifically has an annular shape (ring shape). In the drawing, W represents the wave, F represents an upstream side from which the wave W comes, and R represents a downstream side being the opposite side to the side from which the wave W comes.
FIG. 10 shows a schematic cross-sectional view of the wave power generation device 1X. The wave power generation device 1X includes: a power generator (hereafter, referred to as motor) 4 installed inside the column 2X; and the frame body 5X configured to extend upward from the float 3X and then inserted into the column 2X. The frame body 5X, a rack 6 formed in a portion of the frame body 5X, and a pinion 7 provided in the motor 4 form a power transmission mechanism which transmits motion energy of the float 3X to the motor 4.
Next, an operation of the wave power generation device 1X is described. First, the column 2X of the wave power generation device 1X is substantially fixed to the sea floor with the anchor 31 and the like and is configured to be less subject to the influence of the wave. The float 3X having received the wave moves up and down relative to the substantially-fixed column 2X. The wave power generation device 1X transmits the motion energy of the float 3X as a rotational force to the motor 4 via the power transmission mechanism (the frame body 5X, the rack 6, and the pinion 7) and generates electric power. This configuration allows the wave power generation device 1X to generate electric power by extracting energy from the wave of the sea surface 10 moving up and down.
However, the conventional wave power generation device 1X has a problem that the power generation efficiency is low. The maximum power generation efficiency of the wave power generation device 1X is about 20%. This is because the wave power generation device 1X collects only part of the energy of the wave (incident wave) colliding with the float 3X. Most of the remaining energy of the incident wave is turned into a wave (reflection wave) generated by the collision with the float 3X and into a wave (transmitted wave) formed behind the float 3X, and does not contribute to power generation. Hence, it is difficult to improve the power generation efficiency of the wave power generation device lx.